Blow-out fuse.



vN0. 758,172. PATENTED APR. 26, 1904.

F. B. COREY.

BLOW-OUT FUSE.

APPLIUATION rum) SEPT. 2. 1902.

N0 MODEL. 2 annua -sum 1.

WWWWWWWm/W//// Inventor:

' Fred Siloreg,

mam: PUERS co., Pr-zoimurua, wnsnmm'ou, o e

I witnesses:

No. 758,172. FATENTEDAPR. 26, 1904.

v F.B.COREY.

BLOW-OUT FUSE.

APPLICATION FILED SEPT. 2. 1902.

2 sums-sum 2. I

N0 MODEL.

Inventor: Fr'ecl B.COF'H, v

. fibfifq.

WiCneSSes:

, H: NORRlS PEYERS co" HOTQLITHQ. WASHXNOTON, n, c.

UNITED STATES Y Patented. April as, 1904.

PATENT OFFICE.

FRED B. COREY, OF SCHENECTA DY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACORPORATION OF NEW'YORK.

BLOW-OUT FUSE SPECIFICATION forming part of Letters Patent Era-758,172, dated Apr-H26, 19Q4.

Application filed September 2,1902. Serial No. 121,714. (No model.)

To all whom it may concern:

Be it known that I, FRED B. COREY, a citizen of the United States, residing at Schenectady,

'county of Schenectady, State of New York,

have invented certain new and useful Improvements in Blow-Out Fuses, of which the following is a specification.

The object is to effect an efficient extinguishment of the are formed on melting of the fuse by a simpler and cheaper construction than employed in the best class of such devices.

ed are provided with means auxiliary to the fuse or thermal cut-out itself to prevent lengthening of the arc to the fuse-terminals or the point at which the fuse-wire or fuse-strip is detachably connected with the electric circuit it is to protect. Unless provided with such assisting agency the fuse must bemade sufficiently long to interrupt the arc by themere stretching and consequent increased resistance when the fuse blows. extinguishment, the fuse proper issometimes inclosed in a casing, so that the hotgases and vapors developed when the fuse melts give an expulsive blast toward an openingin the easing, which tends to cut the are. In other cases electromagnetism is employed, the fuse being laid across the magnetic field established by acoil connected in the samecircuit in such a way that the conducting stream of gas formed by the arc when the fuse melts is expelled laterally by the magnetic field until the arc ruptures. My improvements relate more particularly to the last-mentioned type. vices as heretofore constructed require a coil to develop the magnetic field. My invention contemplates dispensing with the auxiliary coil, thus greatly cheapening the cost of the device and conducing toward simplicity and compactness.

In carrying out the invention I partially inclose the fuse in a chamber at the sides of which are placed iron plates which overlap the fuse on either side. The current carried by the fuse itself develops a magnetic field, the

To promote a quick These delines of force being carried by the iron plates and the field at the points where it acts on the fuse being thus intensified. This is one distinctive feature of my invention. distinctive feature is the arrangement of the magnetic circuit in such a way that the-path of least reluctance is always immediately behind the fuse, thus promotinga maximum expulsive force to the stream of vapor constituting the arc. i

In magnetic blow outs as made heretofore a'blow-out coil,as above noted, was employed to furnish the-magnetism, the gap in Devices of this kind ascommonly constructthe magnetic circuit existing around the fuse and "a sufficient distance beyond the same to insure an extinction of the arc. I depart from this practice not only in the elimination of the blow-out coil, but in thearrangement of the magnetic circuit so that the air-gap always exists behind and follows the arc-stream when the fuse blows. This may be simply effected by connecting the plates forward of the fuse with iron yokes or rivets, which bridge the gap forward of the fuse with a good magnetic conductive path which-shunts or'diverts from the space before the fuse all lines of force, concentrating the magnetic field in the space at the rear of the fuse. Thus when the fuse blows the field of force lies to the rearward,

and as the arc-stream is stretched, due to the expulsive force of the magnetic field, this field follows it up until the arc is extinguished.

, My invention is of a general nature and is applicable to fuses of all types and may be usefully employed in connection with inclosed fuses in which the expulsive effect due to pressure is the arc-extinguishing agency. In-such a type the'magnetic bloW-out-efiect acts to assist the flow of gases due to self-generated pressure. In my present application I-show a box type of fuse.

' My invention therefore comprises a thermal cut-out provided with a magnetic-fieldestablished by the fusible element;

It comprises also a thermal cut-out at the sides'of which are mounted plates of good magnetic permeability, such as iron, soarranged that the magnetic flux shifts with the arc Another particularly hereinafter described and will be definitely indicated in the claims appended to the specification.

In the accompanying drawings I have shown an embodiment of my invention in a type of fuse provided with an arc-chute into or through which the arc-stream is driven by the expulsive effect of the magnetic field. As hereinbefore observed, however, my invention is of general applicability to thermal cut-outs of all types.

Figures 1, 2, and 3 illustrate in sectional view a form of fuse especially suitable for use on electric railways under cars in which the fuse and its arc-chute are mounted in a casing provided with a hinged cover. Figs. 4 and 5 show a central longitudinal section and side elevation, respectively, of a modified form of such a fuse; and Fig. 6 is a perspective view of a breech-block to clamp the fuse in its seat.

Referring first to Figs. 1 and 2, 1 represents the base-plate, and 2 the hinged cover,

of a casing adapted to be mounted on a suitable support beneath the car, the mouth being pointed downwardly, so as to direct the are products toward the track. On the baseplate is mounted an insulating-support 3, on which are secured the circuit-terminals 4 4, provided with sockets for the circuit-wires or leads. The terminals are slotted to admit studs 5 5, connected with the fuse-box. These studs may be screwed into the insulatingwalls 6 6 of the blow-out chute, being locked in place by anchor-pins 7 7 driven into holes tapped through the insulating-walls and in terlocking with the screw. The top of each stud carries a nut or screw 8 8, pushed down wardly by helical springs 9 9", bearing against the head of the stud. The studs are provided with flanges or shoulders 10 10, on which the fuse-strip 11 may rest, the latter being provided with slots to permit its being placed on the shoulders and around the studs 5 5. I prefer to close the rear end of the chute by an insulating-wall, this wall being carried by a breech-block 12, slotted at its sides (see Fig. 6) and provided with substantial metal blocks, as 12, which act as good carriers of current from the terminals to the fuse. These are provided with tongues of metal let into the insulating-block 13, which forms the rear wall of the chute, and being anchored in place by pins 14 14, thus forming of the breech-block a substantial rigid structure, which may be pushed into place and withdrawn with case when desired. In renewing the fuse the cover 2 is thrown up after unlatching a spring-detent 15, (see Fig. 3,) the nuts 8 8 are unscrewed, and the breech-block withdrawn from the studs 5 5. The old fuse or pieces thereof is removed and a fresh fuse applied. I have shown this fuse as formed of a piece of sheet metalfor example, aluminium. The breechblock is then restored to its place and the nuts 8 8 tightened. On the outside of the insulating side walls 16 16 of the arc-chute are iron plates 1'7 17, riveted fast to the chute box by iron studs 18 18. These plates are so located, preferably, as to extend both in front and in the rear of the fuse itself, as seen in Figs. 2 and 4. Thus the magnetic flux developed by the flow of current across the fuse flows along the studs 18 18, thus diverting the field from the space in front of the fuse and establishing in the rear of the fuse across the edges or poles of the plates, which project rearwardly of the same, a dense field. When the fuse melts, the conductive Vapor formed by the arc still maintains the establishment of this magnetic field, and as the arc is diverted outwardly toward the open end of the chute, notwithstanding it may arch or bend, the flux across the gap is always maintained immediately behind it in the position of maximum expulsive effort, while in front of it there is no field, sincethe iron yokes or studs 18 18 carry all of the magnetism developed, and these are located outside the chute, or at least outside any arc-stream that may form between the unmeltcd portions of the fuse-strip. In Figs. 4 and 5 the same method of construction is observed. In this type, however, I have shown a modified type of clip for securing the fuse to the terminals. This consists of a hinged piece carrying a stout phosphor-bronze clip 19 and an operatinghandle 20. The terminal is provided with a cooperating face to permit the stout phosphor-bronze spring to be forced firmly against the fuse in securing it in itsseat in the end of the terminal, the construction of which will be clearly understood from an inspection of Fig. 4. The dotted line at 21 indicates the overlapping of the iron plates on the rear side of the fuse.

The fuse operates in the following manner: The current traversing the fusible element developsa magnetic field the lines of force of which are carried by the iron plates and the iron studs or posts which connect these plate in front of the fuse. Thus there is a magnetic circuit established the poles of which and the field of which exist in the gap at the rear of the fusible element. The iron studs form a short circuit for the gap in front of the fuse, thus preventing any considerable amount of flux across the gap at that point. Thus there exists in the rear of the fuse a dense magnetic field which tends to move it forward in the chute. When the fuse melts and the arc forms, this magnetic field drives the gases outwardly, thus stretching the arc and causing it to bow outward but notwithstanding said bowing the field of force follows it until it is extinguished. Thus the field actually follows the arc until the circuit is ruptured and is always in the best relation to extinguish it. The expulsive action is so decided that but a very short section of the fuse is destroyed and the free ends are flexed outwardly toward the sides of the chute.

It is not absolutely essential in all cases that the rear of the chute should be closed, although I prefer to make it so.

What 1 claim as new, and desire to secure by Letters Patent of the United States, is

1. A thermal cut-out provided with termi- -nals for connection with an electric circuit,

and plates of magnetic material at the sides of the fusible element adapted to be polarized by the current passing through said fusible element.

2. A thermal cut-out provided with a blowout chute and pole-pieces mounted at the sides of the fusible element to be polarized by the current in said element.

3. A thermal cut-out provided with a blowout chute, with plates of magnetic material at its sidespolarized only by the field set up by the fuse-current.

1. A thermal cut-out comprising a fuse carrier or support, and plates of magnetic material at the sides of the fuse adapted to be polarized by the current passing through the same, said plates overlapping the fuse on the rear side.

5. A thermal cut-out provided with a magnetic blow-out adapted to be polarized by the field developed around the fusible element, the pole-pieces of said blow-out terminating in an air-gap at the rear of the fuse.

6. A thermal cut-out provided with a magnetic blow-out, and means for establishing a magnetic field principally on one side of the fusible element.

7. A thermal cut-out having a magnetic blow-out polarized by the current in the fusible element, the pole-pieces being so related to said element that the free poles are at one side of the same, whereby the magnetic field which expels the arc-gases follows up the arcstream.

8. A thermal cut-out having a magnetic blow-out polarized by the current in the fusible element and a magnetic field at one side of the fuse, and a path of low reluctance in front of the fuse to direct the line of force.

9. A thermal cut-out having a magnetic blow-out polarized by the current in the fusible element and a magnetic field at one side of the fuse, and a magnetic shunt in front of the fuse to prevent the establishment of a field at that point.

10. A thermal cut-out having a magnetic blow-out polarized solely by the current in the fusible element, and iron plates forming polepieces for said blow-out having free poles at one side of the fuse and iron yokes on the other side laterally displaced from the center of the fusible element.

11. A thermal cut-out having a blow-out chute and a magnetic circuit of high permeability provided with free poles at one side of the fuse, and a low-resistance magnetic shunt in front of the fuse located outside the inner chute-walls.

12. A thermal cut-outhaving an arc-chute open to the atmosphere on one side of the fuse, a fuse-seat at one end of the same, and a removable breech-block to clamp the fuse and close one end of the chute.

13. A thermal cut-out having an arc-chute, iron plates polarized by the current in the fuse, a fuse-seat between the poles, and a removable breech-block to clamp the fuse.

1 1. A thermal cut-out having an are-chute,

iron plates polarized by the current in the.

fuse, a fuse-seat between the poles, and a breech-block to clamp the fuse made of insulating material and provided with metal ends to connect the'fuse With the terminals.

15. A thermal cut-out comprising an arcchute, conducting-studs mounted thereon to receive the fuse, and clamps permanently fixed to the studs to secure the fuse-strip under pressure.

16. A thermal cut-out having an arc-chute and a blow-out polarized by the current in the fusible element, and a casing having an opening in the same direction as the chute, said casing having a laterally-movable cover.

In witness whereof I have hereunto set my hand this 29th day of August, 1902.

I FRED B. COREY.

WVitnesses:

EDWARD WILLIAMS, Jr., GEORGE F. THORNTON. 

